Chemical etching process and system

ABSTRACT

A chemical etching process and apparatus includes a control unit, an etching unit, an etchant supply unit and an air supply unit. The control unit has a programmable electronic device through which various process parameters are input to control the operations of the etching unit, the etchant supply unit and the air supply unit. The etching unit has an etching table incorporated with the etchant supply unit and the air supply unit for providing a proper etching environment for a working object to be etched. The etchant supply unit is equipped with flow control valves and electromagnetic valves respectively for controlling the flow rate and the on/off operation of etchant supply through the control unit. Also, the air supply unit is equipped with flow control valves and electromagnetic valves respectively for controlling the flow rate and the on/off operation of air supply through the control unit.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for etchingdevices and cleaning thin disks, for example semiconductor wafers, glasssubstrates, photomasks and compact disks. More particularly, the presentinvention applies Bernoulli theorem to generate an instantaneous localvacuum effect on a surface of a working object by injecting an airstream, so as to easily remove residues residing in the trenches or onthe surface of the working object. By suitably controlling an etchantspray and an air injection, an etching rate not only can be continuouslykept steady, but also a maximum etching depth can be dramaticallyincreased. Also, the present invention can be used for cleaningsemiconductor devices with an extremely small gate width.

BACKGROUND OF THE INVENTION

In semiconductor fabrication processes, wet etching mainly uses chemicalreactions between a thin film material and a specific solution to removethe thin film not covered by photo-resist. Traditional wet etchingprocess is to first submerse a thin film material into a specificetchant for etching and then control the concentration of the etchant,the etching time, the reaction temperature, the uniformity of theetchant by stirring, and other parameters. However, in the etchingprocess, the etchant is continuously consumed and thus lowers theconcentration thereof and even forms a non-uniform concentrationdistribution of the etchant. Although the non-uniform etchant willincreasingly become uniform through diffusion mechanism or mass transferby stirring, it is relatively slow to get a uniform etchant or hard tocontrol the uniformity thereof. Moreover, after the thin film materialis etched, it needs to be transferred to another place for cleaningresidues and the etchant residing in the trenches or on the surfacethereof. In the meantime, the etchant residing in the trenches thereofstill continues to etch. This will result in an inaccurate control ofthe etching time.

In addition, there is a conventional high-speed-spin etching table usedfor the etching process, which generates a relative movement between asurface of a working object to be etched and airflow there above.According to the Bernoulli effect, when the high-speed airflow flowsover the surface of the working object, a negative pressure even vacuumoccurs on the surface thereof, which can suck out residues residing inthe trenches or on the surface of the working object. However, themagnitude of the negative pressure generated by this method will bedecreasing with approaching to the rotational axis of the working objectdue to a smaller tangential velocity, which is equal to the angularvelocity multiplied by the radius of rotation thereof. Therefore, thenegative pressure might be not enough to suck out the residues residingin the trenches or on the surface close to the center of rotation of theworking object. This method not only needs a driving power to rotate theetching table, but also the etching table is hard to be quicklyaccelerated and decelerated to a desired state due to the inertiaeffect. And it is impossible to spray etchant onto the working objectand suck out the residues simultaneously at a high-speed rotation.Furthermore, more power needs to be input for getting a desired negativepressure or vacuum. Therefore, the method cannot effectively generate anenough negative pressure. And the high-energy consumption will alsoincrease the production cost. The vacuum effect due to a high-speedrotation is proportional to the square of the radius of rotation.Therefore, the etching ability becomes a function of the radius ofrotation, and thus the uniformity of products is highly influenced.

In view of the above problems, the present invention provides with abetter chemical etching process and apparatus.

SUMMARY OF THE INVENTION

An object of the present invention is to provide with a chemical etchingprocess and apparatus, which applies Bernoulli theorem to generate aninstantaneous local vacuum effect on a surface of a working objectthrough injecting an air stream. Furthermore, the present inventionprovides with an etchant spray system and an etching table, which allowsthe working object to be moved in translation or rotation. Also, bysuitably controlling the etching time, the concentration of etchant andthe uniformity of etchant and quickly cleaning residues or etchant onthe surface of the working object can achieve an optimum etching andcleaning result.

To achieve the above objects, a chemical etching process and apparatusaccording to the present invention comprises at least a control unit, anetching unit, an etchant supply unit and an air supply unit. Variousprocess parameters can be input through a programmable electronic deviceof the control unit to control the operations of the etching unit, theetchant supply unit and the air supply unit. The etching unit has anetching table incorporated with the etchant supply unit and the airsupply unit for providing a proper etching environment for the workingobject. Respective flow control valves and electromagnetic valves of theetchant unit and the air supply unit, which are controlled by thecontrol unit, can be used to adjust the etchant flow rate and theairflow rate.

The objects, features and effectiveness of the present invention will bereadily understood to those skilled in the art after reading thedetailed description of the preferred embodiment thereof in reference tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be apparent to those skilled in the art byreading the following description of a preferred embodiment thereof,with reference to the attached drawings, in which:

FIG. 1 illustrates a framework of a chemical etching process andapparatus according to the present invention;

FIG. 2 is a drawing of schematically illustrating a part of the chemicaletching apparatus of the present invention; and

FIG. 3 is a flow diagram of the chemical etching process of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a chemical etching process and apparatus accordingto the present invention comprises a control unit 10, an etching unit20, an etchant supply unit 30 and an air supply unit 40. The controlunit 10 has a programmable electronic device through which variousprocess parameters are input to control the operations of the etchingunit 20, the etchant supply unit 30 and the air supply unit 40. Theetching unit 20 has an etching table incorporated with the etchantsupply unit 30 and the air supply unit 40 for providing a proper etchingenvironment for a working object to be etched. The etchant supply unit30 is an apparatus for supplying etchant, which is equipped with flowcontrol valves and electromagnetic valves respectively for controllingthe flow rate and the on/off operation of etchant supply through thecontrol unit 10. Also, the air supply unit 40 is an apparatus forinjecting air, which is equipped with flow control valves andelectromagnetic valves respectively for controlling the flow rate andthe on/off operation of air stream through the control unit 10.

The etching unit 20 comprises an etching table having a driving gear(not shown in Figures) for moving the working object in translation orrotation. The driving gear has a position control element and a speedcontrol element (not shown in Figures). The control unit 10 respectivelyoutputs a control signal to the position control element and the speedcontrol element for controlling the position and the speed of theworking object.

The control unit 10 outputs a control signal to the flow control valvesand the electromagnetic valves of the etchant supply unit 30 forcontrolling the etchant flow rate and the on/off operation of etchantsupply.

Also, the control unit 10 outputs a control signal to the flow controlvalves and the electromagnetic valves of the air supply unit 40 forcontrolling the airflow rate and the on/off operation of air supply.

Referring to FIG. 2, which illustrates a schematic view of a part of thechemical etching apparatus of the present invention, the etching unit 20comprises an etching table for the etching work of the working object21. The etchant supply unit 30 and the air supply unit 40 respectivelycomprise a spray element 31 and an air nozzle 41 for spraying etchantand injecting air. The spray element 31 and the air nozzle 41 arepositioned in accordance with the etched direction of the working object21.

The etching table of the etching unit 20 has a driving gear (not shown)for tightly fixing the working object 21 so as to drive it rotate.

The spray element 31 has a proper opening of etchant spray, at which theoutlet pressure of the etchant varies with the flow rate thereofsupplied from the etchant supply unit 30.

The spray element 31 can be multiple arranged in proper positions formatching with the etching process of the working object.

Therefore, the multiple spray elements 31 can respectively supplyvarious etchants, buffer solutions or de-ionized water in accordancewith the needs of the etching process.

The air nozzle 41 can be multiple arranged in proper positions above thesurface of the working object 21 for matching with the needs of theetching process. Each of included angles 25 between each of the airnozzles 41 and the corresponding horizontal line 23 thereof can berespectively adjusted depending on actual needs of the etching process.The included angles 25 are between 0-30 degrees.

The air nozzle 41 has a proper opening of air injection, at which theoutlet pressure of air varies with the injected airflow rate from theair supply unit 40.

The direction of the air injection from the air nozzle 41 and thehorizontal line 23 being parallel to the surface of the working object21 form the included angle 25, which can be horizontal.

The opening of the air nozzle 41 can be flat.

The air supplied from the air supply unit 40 can be instead of nitrogengas (N2).

Referring to FIG. 3, which illustrates a flow diagram of a completechemical etching process according to the present invention, step 501 isto install a working object 21 to be etched onto the etching table ofthe etching unit 20. Step 502 is to apply the driving gear of theetching unit 20 to tightly fix and then move the working object 21through the control of the control unit 10. Step 503 is to spray anadequate quantity of etchant and stop the etchant spray after a presettime through the control unit 10 controlling flow control valves andelectromagnetic valves of the etchant supply unit 30. The working object21 will be etched in the period of the etchant contacting with thesurface thereof. Step 504 is to start to inject an adequate quantity ofair in the time t after step 503 through the control unit 10 controllingflow control valves and electromagnetic valves of the air supply unit40. The injected air is used for removing residues residing in thetrenches or on the surface of the working object 21. Step 505 is to stopthe injecting air supply through the control unit 10 controlling theflow control valves and the electromagnetic valves of the air supplyunit 40. Step 506 is to judge through the control unit 10 if therepeated etching time in total attains the required preset etchingtimes. If not, then return to step 503 and continue to perform step 503through step 506. If yes, then proceed to step 507 for further process.Step 507 is to determine through the control unit 10 if the etchantneeds to be replenished. If yes, then replenish the etchant and returnto step 503. If not, proceed to step 508. Step 508 is to stop therotation of the etching table of the etching unit 20 and then take outthe finished working object 21 through the control of the control unit10.

In Step 3, one of the multiple spray elements of the etchant supply unit30 can be selected as spraying buffer solution for meeting with theneeds of the etching process.

In addition, in Step 507, the alternative to replenishing etchant forthe etchant supply unit 30 is to replace with de-ionized water, so thatthe step 503 becomes a cleaning step for cleaning the surface of theworking object 21. The leaning frequency is determined by step 506.

In addition, step 503 through step 507 can be RCA cleaning method.

The features of the present invention are summarized as followings:

(1) A chemical etching apparatus according to the present inventionapplies Bernoulli theorem to generate an instantaneous local vacuumeffect on the surface of a working object through injecting an airstream with a special included angle with the surface of the workingobject, which can easily remove residues residing in the trenches or onthe surface of the working object. In the meantime, the etchant iscontinuously replenished from the etchant supply unit so as to keep theetching rate steady.

(2) Additionally, if the above etching process is changed to be acleaning process, in which etchants shall be instead of cleaningsolutions, residues residing in the trenches or on the surface of theetched object will be cleaned/sucked out and a drying result will befurther attained. The cleaning method can also be used for removingimpurities in the trenches of a wafer for a semiconductor fabricationprocess.

(3) The chemical etching apparatus of the present invention can controlthe etching time and the concentration of etchant through the controlunit so as to attain an intermittent etching reaction. Therefore, anover-etching problem of a conventional wet etching process due toimproper control of the etching time can be avoided.

(4) The method for generating an instantaneous vacuum effect on thesurface of the working object not only can shorten the time to reach avacuum effect but also is favorable to the intermittent etching control.Moreover, the required energy for injecting air is very small relativeto that for driving a high-speed spin etching table.

The chemical etching process and apparatus of the present invention cansufficiently clean the residues residing in the trenches of the surfaceof the working object and thereby avoid the hindrance of etchantapproaching to and contacting with the surface thereof and obtain anoptimum etching depth and an optimum cleaning result with highefficiency, energy saving and the convenience in controlling theintermittent air injection.

The above statement is only for illustrating the preferred embodiment ofthe present invention, and not for giving any limitation to the scope ofthe present invention. It will be apparent to those skilled in this artthat all equivalent modifications and changes shall fall within thescope of the appended claims and are intended to form part of thisinvention.

1. A chemical etching process comprising the steps of: (a) installing aworking object to be etched onto an etching table of an etching unit;(b) spraying an adequate quantity of etchant and stopping the etchantspray after a preset time through a control unit controlling flowcontrol valves and electromagnetic valves of an etchant supply unit; (c)starting to inject an adequate quantity of air through the control unitcontrolling flow control valves and electromagnetic valves of an airsupply unit in a proper time after the start of spraying etchant in step(b), which is used for removing residues residing in the trenches or onthe surface of the working object; and (d) stopping the air injectionafter a proper time through the control unit controlling flow controlvalves and electromagnetic valves of the air supply unit.
 2. Thechemical etching process as claimed in claim 1, further comprising thesteps of: applying a driving gear of the etching unit to tightly fix andthen move the working object through the control of the control unit. 3.The chemical etching process as claimed in claim 1 or 2, furthercomprising the steps of: judging through the control unit if therepeated etching times of step (b) through step (d) attain the requiredpreset etching times; if not, then returning to step (b) and continuingto perform step (b) through step (d); and if yes, then proceeding tonext step for further process.
 4. The chemical etching process asclaimed in claim 1 or 2, further comprising the steps of: determiningthrough the control unit if the etchant needs to be replenished aftercompletion of step (b) through step (d); if yes, then replenishing theetchant and returning to step (b) and continuing to perform the repeatedsteps; and if not, proceeding to next step for further process.
 5. Thechemical etching process as claimed in claim 1 or 2, further comprisingthe steps of: judging through the control unit if the repeated etchingtime in total of step (b) through step (d) attains the required presetetching time; if not, returning to step (b) and continuing to performthe repeated steps; and if yes, then determining if the etchant needs tobe replenished; if yes, returning to step (b) and continuing to performthe repeated steps, and if not, proceeding to next step for furtherprocess.
 6. A chemical etching apparatus comprising at least: a controlunit having a programmable electronic device through which variousprocess parameters are input to control the operations of various units;an etching unit having an etching table and necessary apparatuses forproviding an proper etching environment for a working object to beetched; an etchant supply unit being an apparatus for supplying etchant,which is equipped with flow control valves and electromagnetic valvesrespectively for controlling the flow rate and the on/off operation ofetchant supply through the control unit; an air supply unit being anapparatus for injecting air, which is equipped with flow control valvesand electromagnetic valves respectively for controlling the flow rateand the on/off operation of air stream through the control unit; theetchant supply unit comprising a spray element for spraying etchant,which installation direction shall be incorporated with the etchingdirection of the working object; and the air supply unit comprising anair nozzle for injecting air, which installation direction shall beincorporated with the etching direction of the working object.
 7. Thechemical etching apparatus as claimed in claim 6, wherein the etchantsupply unit can separately supply various etchants, buffer solutions andde-ionized water for the use of the etching process.
 8. The chemicaletching apparatus as claimed in claim 6, wherein the etching table ofthe etchant supply unit comprises a driving gear for tightly fixing andthen moving the working object in translation or rotation, a positioncontrol element and a speed control element respectively for controllingthe position and speed thereof, which are controlled by the control unitoutputting control signals thereto.
 9. The chemical etching apparatus asclaimed in claim 6, 7 or 8, wherein the air supply unit comprisesmultiple air nozzles arranged in proper positions above the surface ofthe working object for meeting with the needs of the etching process,and each included angle between each of the air nozzles and the surfaceof the working object can be respectively adjusted upon actual needs,which can be 0 degrees, namely in horizontal.
 10. The chemical etchingapparatus as claimed in claim 6, wherein an opening of the air nozzlecan be flat.
 11. The chemical etching apparatus as claimed in claim 6,wherein the air supplied from the air supply unit can be instead ofnitrogen gas (N2).
 12. A method for cleaning residual etchants residingon the surface of an etched working object by specific etchants, and theimprovements comprising: a high speed air stream being injected acrossthe surface of the working object so as to generate a relative pressuredifference on the surface thereof and thus suck out the residualetchants.
 13. The method as claimed in claim 12, wherein the directionof the air injection is parallel to the surface of the working object.14. The method as claimed in claim 12, wherein an included angle betweenthe air injection and the surface of the working object is between 0-30degrees.
 15. A method for cleaning residues residing in the trenches ofa wafer, and the improvements comprising: a high speed air stream beinginjected across the surface of the wafer so as to generate a relativepressure difference on the surface thereof and thus suck out theresidues.
 16. The method as claimed in claim 15, wherein the directionof the air injection is parallel to the surface of the wafer.
 17. Themethod as claimed in claim 15, wherein an included angle between the airinjection and the surface of the wafer is between 0-30 degrees.